Csillagkeletkezés

Csillagkeletkezés, in English star formation, is the astrophysical process by which dense regions within molecular clouds in interstellar space collapse to form stars. These molecular clouds are vast, cold, and dark collections of gas, primarily hydrogen and helium, along with dust. The process begins when a portion of a molecular cloud becomes sufficiently dense to overcome its internal pressure and begin to gravitationally collapse. This increased density can be triggered by various events, such as shockwaves from a nearby supernova explosion or the passage of a spiral arm of a galaxy.

As the cloud collapses, it fragments into smaller clumps. Each clump continues to contract, and its core heats up due to the conversion of gravitational potential energy into thermal energy. This collapsing, heating clump is known as a protostar. The protostar is surrounded by a rotating disk of gas and dust, from which planets may eventually form.

The protostar grows by accreting material from its surrounding disk. Eventually, the core of the protostar becomes hot and dense enough for nuclear fusion to begin. This is the process where hydrogen atoms fuse to form helium, releasing an immense amount of energy. This energy creates outward pressure that balances the inward pull of gravity, stabilizing the star. At this point, the protostar becomes a main-sequence star, like our Sun. The remaining gas and dust in the surrounding disk can coalesce to form planets, asteroids, and comets, completing the star system formation.